Conventionally, in a mobile communication system such as a long term evolution (LTE), cell selection of selecting a cell (base station) to which a terminal is connected based on the wireless quality or for which the terminal waits (camps on, idles) (see, for example, Published Japanese-Translation of PCT Application, Publication No. H7-509826, International Publication No. 2011/087022, Japanese Laid-Open Patent Publication No. 2011-124732, and International Publication No. 2010/134202). Carrier aggregation (CA) is also known in which communication is performed using a primary cell and a secondary cell at the same time.